DESCRIPTION: Spinal muscular atrophy (SMA) is a neurodegenerative disease and the most common genetic cause of infant mortality. This disease is characterized by deterioration of motor neurons in the spinal cord and atrophy of skeletal muscles. SMA is caused by loss of the Survival of Motor Neuron (SMN1) gene. At present, the precise function of SMN is not known. The protein is thought to have roles in both RNAP II transcription and pre-mRNA splicing. Recent studies have indicated that these two steps in gene expression are functionally coupled to one another, but no proteins involved in this coupling are known. A central goal of my project is to determine the function of SMN in gene expression. To accomplish this goal, I plan to establish the first in vitro strategy for combining RNA interference (RNAi) with a system for coupling RNAP II transcription to splicing. To achieve this goal, I will use a new robust mini-nuclear extract procedure that I am currently developing for coupling transcription and splicing. The role of SMN in transcription, splicing and/or coupling will then be tested in this system using RNAi. My next central goal is to identify novel proteins that interact with SMN in the nucleus. The mini-nuclear extract procedure to will then be used to determine the roles of SMN-interacting proteins in transcription, splicing, and/or coupling. Finally, in order to gain insights into why SMN deficiency specifically affects neurons, I plan to apply these approaches for identifying and analyzing the role of neuronal-specific SMN-interacting proteins in transcription, splicing, and/or coupling. These studies provide a powerful new approach for elucidating the function of SMN as well as other proteins that cause genetic disease due to defects in gene expression. In addition, the new system will be a general strategy for identifying factors that function in coupling transcription to splicing. I anticipate that this work will provide important new insights into the molecular mechanisms leading to SMA as well as identify potential therapeutic targets for the disease. [unreadable] [unreadable] [unreadable]